JPH0779376B2 - Communication terminal - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an extension communication system between terminals on the same bus connected to an ISDN line and a communication terminal used in this communication system.

Conventional technology ISDN basic interface, 64kbps B channel 2
The book and one D channel of 16 kbps are used for communication. The D channel is used as a conventional signal channel for line control, and communication is performed based on a communication protocol called LAPD. The communication frame consists of a service access point identifier (SAPI), a terminal termination identifier (TEI) assigned to each terminal to identify each terminal from the public network side, and a C / R bit to identify whether the frame is a command or a response. It has an address part composed of. At the time of line connection, communication is performed via the public network by using the call control SAPI value '0' and the TEI value of the terminal itself as the address of the transmission frame. Also, the terminal side is C / R
The command is sent to the public network side with the bit set to "0", and the response is sent to "1". As a connection form of a premises terminal, a plurality of terminals may be connected to one passive bus. A plurality of terminals connected to the same bus identify the presence or absence of D-channel communication by monitoring the echo bit returned from the line terminating device as the return of the D channel. However, only the monitoring is performed and the echo bit is not captured as an information signal.

However, with the line control method and the communication terminal as described above, it is impossible to directly take in the D channel data sent from another terminal connected to the same bus. Therefore, in order to perform communication (extension communication) between terminals on the same bus, only a private branch exchange such as a PBX or a method via a public network using a switching function on the public network can be used. The present invention has been made in view of the above problems, and provides an extension communication system and a communication terminal having an extension communication function capable of communicating between terminals on the same bus without using an exchange. With the goal.

Means for Solving the Problems In order to solve the above problems, the present invention newly defines the value of SAPI for extension communication between terminals connected to one bus connected to an ISDN line, and For extension communication
By setting the TEI and using the SAPI value for extension communication and the TEI value for extension communication as the address of the line control signal frame, an extension communication method for performing extension communication between terminals on the same bus using the D channel is there. Further, according to the present invention, the communication control means for controlling the input / output of communication information and the channel to be received as the line control signal are switched so that the D channel is used during the external communication and the echo bit is used during the internal communication. An extension switching means, an outside / extension designating means for designating an outside / extension and notifying the communication control means,
Communication equipped with an echo bit monitoring means for monitoring the echo bit and notifying the outside / extension switching means when a frame having the SAPI value for the extension communication and the TEI value for the extension communication of its own terminal as an address is received It is a terminal.

Effect The present invention, in the communication terminal having the above-described configuration, notifies the terminal on the same bus that the communication is the extension communication by using the SAPI value for the extension communication in the address of the line control signal frame, and the extension communication is performed for each terminal. By giving it a TEI value, it is possible to specify any terminal on the same bus. Also, D
By allowing information to be transmitted on the channel and received on the echo bit, it is possible to perform D-channel extension communication between arbitrary terminals on the same bus.

Embodiment An embodiment of the present invention will be described below with reference to the drawings. First
FIG. 1 is a block diagram of a communication terminal with an extension communication function according to an embodiment of the present invention. In FIG. 1, 1
Is a communication terminal connected to an ISDN line, 11 is an information management unit that manages communication information, 12 is a communication control unit that controls input / output of communication information, and 13 is an input channel as a line control signal, which is either an external line communication or an internal line communication. The external / extension switching unit for switching between the D channel and the echo bit depending on
14 is an external / extension designating unit that specifies whether to perform internal communication or external communication, and 15 monitors the echo bit, and a frame having an SAPI value for internal communication and a TEI value for internal communication of the own terminal as an address. This is an echo / bit monitoring unit that performs identification. FIG. 2 is a conceptual diagram of information transmission by the extension communication system in the embodiment of the present invention. In FIG. 2, reference numerals 21 and 22 denote communication terminals connected to the same passive bus, which are equivalent to the communication terminal 1 shown in FIG. Reference numeral 23 is a line terminating device. Regarding the extension communication system using the communication terminal of this embodiment configured as described above,
The operation will be described below. First, for extension communication, use a SAPI value that is not yet defined as an ISDN standard (for example, '8').
The extension TEI value (for example, "1" for the communication terminal 21 and "2" for the communication terminal 22) is set in advance for each terminal on the same bus as the SAPI value. In the communication terminal 21, when the external / extension designating unit 14 designates the extension communication, the communication control unit 12 is notified that the extension communication will be performed. When the communication control unit 12 receives the extension communication from the outside / extension designating unit 14, the address of the D channel frame to be transmitted for line control is set to the extension communication SAPI value '8' and the extension of the destination communication terminal 22. It is configured by the communication TEI value '2' and C / R bit '0'.
The D channel signal transmitted from the communication terminal 21 reaches the line terminating device 23 through the passive bus, is transferred to the echo bit, and returns on the passive bus. In the communication terminal 22, the echo bit monitoring unit 15 receives the echo
When the bit is monitored and a frame having the SAPI value for extension communication '8', the TEI value for extension communication of its own terminal '2' and the C / R bit '0' in the address is recognized, it is the command reception of extension communication. To the outside / extension switching unit 13. When the external / extension switching unit 13 receives the notification of the extension communication reception from the echo bit monitoring unit 15, the echo bit is transmitted to the communication control unit 12 instead of the D channel. When the communication control unit 12 receives a frame having the extension communication SAPI value of "8", the D channel frame address is set to the extension communication SAPI value of "8", the extension communication TEI value of the own terminal is "2", and C / It consists of R bit '1' and sends a line control signal as a response. The subsequent call control means uses LAPD which is the ISDN line protocol as it is. After the call is set up between the communication terminals 21 and 22, the information from the information management section 11 is transmitted from the communication control section 12 using the D channel, and the information is received using the echo bit for communication. The control unit 12 notifies the information management unit 11 of the received information. As described above, according to this embodiment, the extension communication SAPI value '8' and the extension communication TEI value are used as the address of the line control signal, and when the command frame is transmitted,
Set the C / R bit to "0" and set C when transmitting a response frame.
By setting the / R bit to "1", the terminals connected to the same passive bus are notified of the extension communication, and the extension communication can be performed. In addition, by providing the communication terminal with means that can switch to use the echo bit for the receiving channel during extension communication, it is possible to connect terminals that are connected in the same way without special circuit switching equipment outside the terminals. Communication becomes possible.

EFFECTS OF THE INVENTION As is clear from the above description, the present invention provides the following between terminals connected on one bus connected to an ISDN line.
SAPI value for extension communication is newly specified, and extension communication is performed for each terminal.
By setting the TEI value and using the SAPI value for extension communication and the TEI value for extension communication as the address of the line control signal frame to perform line control, the conventional IS
By changing only the address part of LAPD, which is a DN communication protocol, it is possible to notify the terminal on the same bus that it is an extension communication and to specify the destination terminal. Further, the communication control means for controlling the input / output of communication information and the channel for receiving the line control signal are the D channels during the external line communication,
During extension communication, an outside / extension switching means for switching to use an echo bit, an outside / extension designating means for designating an outside / extension and notifying the communication control means, an echo / extension
An echo / bit monitoring means for monitoring the bit and notifying the outside / extension switching means when the frame having the SAPI value for extension communication and the TEI value for extension communication of the own terminal as an address is received is connected to the ISDN line. It is possible to transmit information on the D channel and receive the information on the echo bit by providing the communication terminal which is capable of performing the D channel extension communication between arbitrary terminals on the same side. Is to have.

[Brief description of drawings]

FIG. 1 is a block diagram of a communication terminal with an extension communication function in an embodiment of the present invention, and FIG. 2 is a conceptual diagram for showing information transmission by an extension communication system in an embodiment of the present invention. 1 ... communication terminal, 11 ... information management unit, 12 ... communication control unit, 13 ... outside / extension switching unit, 14 ... outside / extension designation unit, 15 ... echo / bit monitoring unit, 21, 22 ...... Communication terminal, 23 …… Line terminating equipment.

Claims (1)

[Claims] 1. A service access point identifier value for extension communication is newly defined between terminals connected on one bus connected to an ISDN line, and a terminal termination identifier value for extension communication is set for each terminal. Then, by using the extension communication service access point identifier value and the extension communication terminal termination identifier value as the address of the line control signal frame, D
A communication terminal used in an extension communication method for performing extension communication between terminals on the same bus using a channel, which controls input / output of communication information, and commands during extension communication are terminal termination identifiers for extension communication of the other party. A D channel frame having an address field containing a value and C / R bit '0' is transmitted, and the response is a terminal termination identifier value for extension communication of the own terminal and an address containing C / R bit '1'. A communication control means for transmitting a D channel frame having a field, and an external / extension switching means for switching a channel to be received as a line control signal so that the D channel is used for external communication and the echo bit is used for internal communication. Specify the outside / extension,
An external / extension designating means for notifying the communication control means and an echo / bit monitoring means for monitoring the echo bit and notifying the external / extension switching means when the service access point identifier value for extension communication is received are provided. A communication terminal characterized by the above.